Thinset Mortar for fake rocks?

[momerath]

So, I've been scouring the forums to find some solid info on DIY fake rock work. I have a project coming up that will incorporate a rock wall/water feature, and I'm trying to figure out just which type/brand of mortar to use.
I've seen Ultraflex 2 mentioned a lot, and tile grout in general, but I am concerned about using this particular product because it clearly states "Do not use for installations subject to prolonged water
immersion (swimming pools, gang showers, hot tubs,
fountains, etc.)" yet people are using it for water features, which is my intended use as well.
However, Ultraflex 3 is safe after a 28 day curing period, and Granirapid can be safely submerged after only 72 hours. (Both are from the same company, MAPEI).
I have also considered Habacrete, but it is expensive, and I would have to order it online.
So, for all you faux rock builders out there, exactly what type of mortar are you using and why?

[Vivweaver]

I've always seen just generic motar mix used. There's the stuff they use for pools, but even with the 'special' mortar, the masons need to add a special epoxy to sink into it. Long story short, I advise basic mortar.

[beckdg]

here's the deal in plain english for dummies like me. you can use any mortar you want. you can use floor leveler, crack fixer, bonding agent, grout, etc.. keep in mind though what your overall plans are. each type of mortar, etc. will have different properties and different reasons for use. if you are wanting to make something waterproof or have water over it and something potentially toxic or that will erode below than waterproof is obvious.

you mention habacrete... it's a nice idea for those who are ill or un informed but is far from necessary in ANY case! it is NOT waterproof. the only thing it claims that's worth pointing out is it is ph balanced and ready to be used as soon as it's cured. that's fine and dandy if you don't have to wait for 2 weeks for silicone to stop stinking and some time for any plants you might add to establish themselves before adding your animals. btw... that's also a good time to familiarize yourself with your setup before you put the animals in and have to disturb them every couple days to change or fix things.

here is another point to ponder with mortar. think of it's primary use and any other more likely uses it might be marketed for or sold for. the instructions on the bag will be according to that as well as anything else the company who manufactures the product might think to be a liability.

regular mortar like the thinset contains lye and a few other things. that's most likely where the problem lays here. lye leaches and creates a nice spike in ph. until this is balanced it's best not to have animals playing in that water... even us. from experience i can say that mixing mortar all day will burn and dry your skin up bad.

the good thing! vinegar is about the opposite ph of mortar. therefore soaking with vinegar can for the most part neutralize ph if it is soaked well enough. the rest can be leached with water. the easiest way is submersing with or without pumps running and swapping out the water till the water ph matches the ph to the source water (tap, etc.).

now that that's out of the way any concrete surface is going to need something somewhat rough to adhere to. you will want to start thin and work to just thicker than soupy. that's what works best for me. if you go with thinset i would make sure i make it thick because thinset tends to crack pretty easy. on that note drying with extreme airflow usually works fine. drying with heat usually nets a do over because of cracks.

so to rehash... all these options will work well. what you have to consider now is what do you want to spend and how much work are you willing to do to avoid busting your budget. you're probably gonna anyway. i do with every animal. once you figure that out go to home depot and read the labels for your self and you will be much more pleased with your end product.

good luck and keep the questions coming.

[momerath]

I am in no way opposed to taking the time to allow the mortar to cure, and balance the Ph. Every tank I've done before has taken much longer than I intended as I always play it safe with my babies and take my time. I've done plenty of tanks with variations of 'Great Stuff', but this will be my first endeavor into rock work with mortar.
So is the general consensus to regular cement mortar instead of the thinset or tile grout mortar? I guess I just got hung up on the tile grout because it's about the only thing I've seen mentioned by brand name on the forum and it stuck in my head. I have NO knowledge of mortar other than what I've read so far in this forum, and I have learned SO MUCH already.
Please keep the suggestions coming!

[beckdg]

well i just finished a project myself. i got a couple hermit crabs from the fair because i was not bringing home goldfish i didn't have a tank ready for for my 5 yr old. i used an old broken tank so i threw on a background to cover where the glass was shattered.
for this project i used commercial grade quickrete vinyl concrete patcher. the reason i used it was because of price and i figured since it's a patcher it'll hold up better than mortar. also the properties of vinyl was a seller for me. concrete normally doesn't take shrinking and swelling too well when it's thin whereas the vinyl will.
it comes in a yellow plastic can with a black lid in home depot. the cost was around $6 for the 10 lb can (about 1-2 gallon size).

here is a pic of how it looks so far:
100_1677.jpg
i will be making a water bowl too to get rid of the gaudy bowl.

this is basically what i did... pretty easy... i did add a third layer and dab with the paint brush for a rough/random finish... YouTube - how to make a DIY aquarium background PLEASE RESPOND

[momerath]

Nice and simple! I love your basic techinque. Thank you very much for sharing that video!

[beckdg]

thank you and you're welcome.

[brp4e.]

make sure you're not using mortar, use concrete. Mortar will dissolve if you spray water or any other liquid onto it.

[beckdg]

the only difference between mortar and concrete is concrete has rocks in it. to make concrete you take mortar and add rocks... to make it stretch add sand. i did this for a living for a while... hence the mention of mixing it all day, dry and cracked hands, etc..